CG_Union — Computes the union of two geometries
geometry CG_Union( geometry geomA ,  geometry geomB );
Computes the union of two geometries.
Performed by the SFCGAL module
                 
               | 
              |
| 
                 NOTE: this function returns a geometry representing the union.  | 
            
Availability: 3.5.0
            
 Questo metodo richiede il backend SFCGAL. 
SELECT CG_Union('POINT(.5 0)', 'LINESTRING(-1 0,1 0)');
                cg_union
                -----------
                LINESTRING(-1 0,0.5 0,1 0)
                (1 row)